The　structure　of　miniature　circuit　breaker　is　complex　and　there　are　many　parts　in　it.　Electromagnetic　photothermal　phenomena　produced　in　process　of　motion　involve　multiple　physical　fields.　Therefore,　traditional　analysis　method　can＇t　realize　the　optimization　of　breaking　speed　for　miniature　circuit　breaker.　When　carrying　out　optimization　design,　multiple　objectives　will　conflict　with　each　other,　and　it　is　easy　to　fall　into　local　optimization,　leading　to　the　failure　of　optimization.　Aiming　at　the　above　problems,　an　improved　PSO　algorithm　is　proposed　to　optimize　the　breaking　speed　of　circuit　breakers.　ADAMS　secondary　development　function　is　used　to　establish　the　optimal　model　of　UEB63　miniature　circuit　breaker;　On　the　basis　of　standard　PSO　algorithm,　catfish　effect-cloud　mode　strategy　is　introduced　to　improve　the　algorithm,　and　test　the　algorithm　effect;　Select　best　parameter　design　scheme　among　the　feasible　solutions.　Simulation　and　experimental　results　show　that　the　modified　particle　swarm　optimization　algorithm　can　improve　breaking　speed,　and　the　breaking　performance　of　the　circuit　breaker　is　improved.　©　2019　IEEE.